As a part of processes for manufacturing a semiconductor device such as an MPU (Micro Processing Unit), a DRAM (Dynamic Random Access Memory), and the like, an oxide film that contains a predetermined element is often formed on a substrate by alternately performing, a predetermined number of times, a process of forming a predetermined-element-containing layer on the substrate by supplying a precursor gas containing a predetermined element such as silicon or the like into a process chamber accommodating the substrate therein and a process of oxidizing the predetermined-element-containing layer by supplying an oxygen-containing gas and a hydrogen-containing gas into the process chamber which is kept under a pressure lower than the atmospheric pressure.
However, if the process of forming the oxide film is performed, a base film existing on a substrate surface may be oxidized during the process of forming the oxide layer. This is because oxidizing species generated in the process chamber in the process of oxidizing the predetermined-element-containing layer has a strong oxidizing power. Oxidation of the base film significantly occurs if the base film is formed of a material which is easily oxidized, such as silicon or the like. The oxidation of the base film often deteriorates the quality and throughput of semiconductor devices.